Medical endoscopes were first developed in the early 1800s and have been used to inspect inside the body. A typical endoscope consists of a distal end comprising an optical or electronic imaging system and a proximal end with controls for manipulating the tools and devices for viewing the image, with a solid or tubular elongate shaft connecting the ends. Some endoscopes allow a physician to pass tools or treatments down a hollow channel, for example, to resect tissue or retrieve objects.
Over the past several decades, several advances have been made in the field of endoscopy, and in particular relating to the breaking up of physiologic calculi in the bile ducts, urinary tract, kidneys, and gall bladder. Physiological calculi in these regions may block ducts and cause a patient a substantial amount of pain and therefore must be broken down and/or removed. Different techniques have been developed to break up stones, including ultrasonic lithotripsy, pneumatic lithotripsy, electro-hydraulic lithotripsy (EHL), and dissolution of calculi using green light, YAG, or holmium lasers.
A number of rigid solid or tubular shaft-based lithotripsy devices that use ultrasonic or pneumatic energy to break the stone into smaller pieces for easier removal from the patient's urologic system have been developed. For example, the Olympus LUS-2, the Gyrus ACMI Cyberwand, and the Swiss Lithoclast are such devices. Ultrasonic or acoustic frequency energy is transmitted down a stiff metal shaft and delivered by contact to a kidney stone. Ultrasonic lithotripters require tuned shafts and the effectiveness of these lithotripters depend on their ability to maintain resonance down the length of the shaft (i.e. ultrasonic energy does not travel well around bends or turns). Probe bending can dissipate enough heat to seriously damage adjacent tissue, in addition to the loss of energy transfer at the tip of the probe.
For procedures performed with a tubular shaft device, suction of liquid and debris during the lithotripsy procedure is possible via the center of the tubular shaft. Some devices incorporate and deliver a lower frequency energy component to the kidney stone either through the same shaft or via a second shaft; this second shaft is usually coaxial to the ultrasonic energy shaft (i.e. the Cyberwand). This secondary, lower frequency shows evidence of improving the stone breaking efficiency over a solely ultrasonic energy approach.
The use of such a lithotripsy device requires that the stone being broken is pressed up against some surface, usually an inner wall of the kidney, in order that the vibrational energy can be sufficiently delivered to the stone surface to break it up. Some devices now on the market offer a combination of a lithotripsy shaft and a stone basket (i.e. the Swiss Lithobasket) where the lithotripsy shaft is incorporated into the center of the lithotripsy basket shaft and emerges into the center of the lithotripsy basket. The Swiss Lithobasket allows for the ability to apply the Swiss Lithoclast pneumatically driven shaft to a kidney stone contained in the associated basket, however this device is limited in that no suction is possible through the lithotripsy shaft.
Laser lithotripsy involves the use of laser fibers to effectively break up stones in virtually any area of the urinary system. When used with flexible ureteroscopes, laser fibers can bend around corners and access kidney stones in the lower pole of the kidney. A problem with this approach is that laser fibers have been known to break inside the working channel and damage flexible ureteroscopes. Some techniques have been developed for laser lithotripsy using semi-rigid ureteroscopes to make stones accessible by a straighter path. However, laser lithotripsy in general has a much more expensive start-up cost vs. ultrasonic lithotripsy due to the relative capital equipment costs.
The size, stiffness and length of the straight shafts in much of the existing ultrasonic lithotripter technology only allow for the use of such lithotripters with large shafts in percutaneous procedures, i.e. direct access to stones in the kidney through a small incision in the patient's back and on into the kidney itself. Percutaneous access to physiological calculi with laser lithotripsy provides one solution to prevent breaking and damage of flexible endoscopes during laser or ultrasonic lithotripsy. However, this approach requires more intensive anesthesia and can have longer recovery times for the patient.
Electrohydraulic Lithotripsy (EHL) provides a similar ease of access via a flexible endoscope as laser lithotripsy with generally lower cost, but with also generally lower stone fragmentation efficiency as well as some concerns about local shockwave effects on nearby tissue.
Additionally, a predominant majority of current lithotripsy shafts are distally terminated smoothly and perpendicular to the shaft axis. This smooth, flat surface, while providing more protection to soft tissue because of the inherent smoothness, can make it extremely easy for the activated shaft to slip off a stone, or for a stone to slide out from beneath the vibrating smooth tip and thus prolong the stone breaking procedure as the physician “chases” the stone around.
Despite the approaches discussed above, there is still a need for an endoscope device that allows for reliable functionality and easy access of a lithotripsy device or shaft to physiologic calculi with a rigid, semi-rigid or semi-flexible shaft of an endoscope, without the need to approach the physiologic calculi percutaneously, by providing a substantially straight or minimally curved entry channel for a rigid, semi-rigid or semi-flexible lithotripsy shaft from an entry port to distal tip of an endoscope. In addition, there is a need for a lithotripsy shaft with guide features to facilitate passage of a stone retrieval device there through such that the stone retrieval device is able to retrieve a stone and place it in line with the substantially straight shaft lithotripter.